Genetic demography of the amazonian Ticuna Indians

The Ticuna Indians of Brazil are now a largely acculturated and integrated tribe, situated for the most part in villages along the Solimões river. Demographic information collected in eight of their villages is reported here. For five of them detailed data concerning migration, fertility and mortality were obtained. They are characterized by a relatively large mobility, high fertility (mean number of livebirths per female of age 40 or more: seven), low (2·5%) frequency of sterile couples, and relatively low mortality for groups living at this cultural stage (25% of deaths before the age of reproduction). This low mortality, and a relatively small variance in the number of live-born children in completed families, lead to the lowest index of opportunity for selection obtained thus far in populations of South American Indians (0·54).     

Oxidative damage in the guinea pig hippocampal slice

Free radicals and active oxygen compounds are implicated in brain ischemia and head trauma. Previous studies have shown that free radicals, generated by radiation and through the Fenton reaction, produce both synaptic and postsynaptic damage in the hippocampal brain slice. To evaluate the contribution of oxidation to the observed damage, the actions of the oxidants, chloramine-T and N-chlorosuccinimide (NCS), were studied on electrophysiological responses in the hippocampal slice isolated from the brains of guinea pigs. Electrical stimulation of afferents to neurons of the CA1 region of hippocampus evoked a population postsynaptic potential (population PSP) in the dendritic layer and a population spike in the cell body layer. Chloramine-T (25-500 microM) and NCS (750-4000 microM) decreased the population spike in a dose-dependent manner (ED50 congruent to 125 microM and 1100 microM, respectively). Input/output curves revealed that both the population PSP were significantly reduced with both oxidants; but, the ability of the population PSP to produce a population spike was not impaired. These studies suggest that oxidation reactions can account for the synaptic component of the damage produced by free radicals but can not account for the postsynaptic effects.     

Efficiency of homocysteine plus copper in inducing apoptosis is inversely proportional to gamma-glutamyl transpeptidase activity.

Hyperhomocysteinemia represents an independent risk factor for atherosclerosis, but the mechanisms leading to cellular dysfunctions remain unknown. Using ECV304 cells, we found that homocysteine (Hcy) plus copper (Cu2+) induced cytotoxic effects: loss of cell adhesion, increased permeability to PI, and the occurrence of morphologically apoptotic cells. This form of apoptosis, inhibited by Z-VAD-fmk, was associated with a loss of mitochondrial potential, a cytosolic release of cytochrome c, activation of caspase-3, degradation of poly(ADP-ribose)polymerase, and internucleosomal DNA fragmentation. However, the ability of Hcy plus Cu2+ to induce apoptosis decreased when the pretreatment culture time increased. As a positive correlation was found between the length of time of culture before treatment and the enhancement of gamma-glutamyl transpeptidase (gamma-GT) activity, we asked whether gamma-GT was involved in the control of Hcy plus Cu2+-induced apoptosis. Therefore, ECV304 cells were treated with either acivicin or dexamethasone, inhibiting and stimulating gamma-GT, respectively. In ECV304 cells and human umbilical venous endothelial cells, acivicin favored Hcy plus Cu2+-induced apoptosis whereas dexamethasone counteracted the apoptotic process. As acivicin and dexamethasone were also capable of modulating cell death in ECV304 cells treated with antitumoral drugs, our data emphasize that the involvement of gamma-GT in the control of apoptosis is not restricted to Hcy but also concerns other chemical compounds.